WAITING FOR THE
SHADOW

SOLAR AND LUNAR
ECLIPSE OBSERVING

Note : This is an article
about how to view the November 2012 Total Solar eclipse in Australia.
If you want information about the next annular solar eclipse
visible across Australia on May 10th, 2013 click here.

This
page has been written as an introduction to solar eclipses and a
description of what you can expect to see from the Cairns region on November 14th. It is aimed at first time
eclipse chasers. A more detailed description of
the lay of the land and a lot more information about the eclipse is
available for experienced eclipse chasers. Novices are advised to read
this introductary document first.

Few people who witness a total
eclipse of the Sun, fail to be deeply moved by the experience.
Afterwards, they search for superlatives. Phrases such as, "the
most spectacular thing I've ever seen" or "mother natures
great show," flow from the lips of "eclipse chasers."

A total eclipse will be visible
from Cairns beginning just after sunrise on 14th November 2012.
Why not combine the experience of this great spectacle of nature
with a visit to a hotspot for some of Australia's iconic attractions?

A total solar eclipse occurs when
the Moon passes between the Sun and the Earth. Total solar eclipses
can only occur at some New Moon's but they don't occur every
New Moon because the Moon's orbit is inclined 6o to
the Earth's obital plane. Eclipses only occur when the Moon passes
through the Earth's orbital plane at New Moon otherwise the shadow
misses the Earth(as illustrated in the diagram below).

Eclipses on the Australian
ContinentMany people
think they've seen a total solar eclipse when in fact they've seen a
partial eclipse. Partial solar eclipses can be seen from a very wide
geographic area. Most adults in Australia will have been able to see a
partial solar eclipse at some point during their lives. Deep partial
eclipses, deep enough to cause noticeable darkening of the sky.
However, total solar eclipses must be viewed from within a relatively
narrow path defined by the Moon's travelling shadow. This path usually
covers about 1% of the Earth's surface with 2/3rd's of this being over oceans. Total eclipses occur on average about once every 18 months. Because
most of the Earth's surface is either ocean or remote desert
or wilderness, you usually have to go to a lot of trouble to
see one. From any one fixed location, a total solar eclipse can be
seen about once every four hundred years. Over the past eighty
years only three total eclipses have been visible from the Australian
continent. A total eclipse in 1974, could only be seen from southwest
W.A. near Albany. The most widely seen event was in October 1976
when the Coorong, Mt Gambier, most of southern Victoria and the
southest corner of NSW saw a total eclipse. The bigger towns
included Mt Gambier, Bendigo, Ballarat, Geelong, Melbourne and
Bombala among many others. In December 2002, a total eclipse
was visible inside a narrow 20km wide path over very remote areas
of South Australia between Ceduna and Cameron Corner. After the
2012 Cairns eclipse, the next opportunity to see a total eclipse
in Australia is from remote Exmouth, W.A. in 2023. In July 2028,
a total eclipse will cross the whole continent starting in the
Kimberley crossing many regional towns and centres and finally
being visible across much of Sydney.

The eclipse date and
timeThere is some confusion
over the date of the eclipse because some documents list the
eclipse occurring on November 13th, 2012 while others will say
November 14th, 2012. Both are quite possibly correct. It is standard
practice to document astronomical events in 24 hour universal
time. Universal time is the time (and date) at Greenwich Observatory
in England. This allows astronomical observers anywhere in the
world to read a document and easily work out the time of the
event at their own location without confusion. You will see the
letters UT or UTC printed with the time when this is the case.
In universal time, the total eclipse begins at 20:38UT on November
13th, 2012. Any resource that is written for astronomers will
use this standard. You need to add 10 hrs to convert UT to Australian
Eastern Standard Time (EST) which is the local time zone in Cairns.
Expressed in Australian EST or local time, the total eclipse
begins in Cairns at 6:38 am on November 14th, 2012.

Location

Cairns
Lagoon

Duration of total
eclipse

2m00.2s

Partial Eclipse Begins

05 45 am (EST)

Total Eclipse Begins

06 38 33 am (EST)

Mid-Eclipse

06 39 33.4 am (EST)

Total Eclipse Ends

06 40 33.7 am (EST)

Partial Eclipse Ends

07 40 20.7 am (EST)

The eclipse path
The first point of contact of the Moon's shadow with the Earth's
surface occurs north east of the Kakadu National Park, in a line
extending northeast of Ubirr Rock. The shadow travels east across
Arnhem Land, crosses into the Gulf of Carpentaria coast at the
north end of Blue Mud Bay. It strikes land again on Cape York
Peninsula near Wallaby Island. The centreline crosses the Eastern
coast 30km north of Cairns about halfway between Cairns and Port
Douglas. After that it crosses Green Island before heading south
east across the Pacific where it doesn't touch land again.

The 2012 total eclipse
can be seen along the coast from a 140 km wide path. The path
crosses the coast at an angle so that the 140km wide path covers
a 200km swathe of coastline between Innisfail in the south to
Cedar Bay National Park about half way between Cape Tribulation
and Cooktown. Outside this area, a partial eclipse only will
be visible. Just outside the total path, for example south Innisfail,
a 99.9% partial eclipse is visible. Be in no doubt, a 99.9% partial
eclipse is not almost the same as the spectacle of a total eclipse.
If you live near the edge of the path, get in the car and drive
into the path of totality. Anywhere between Gordonvale and Port
Douglas on or near the coast are the best places to see the eclipse.
The duration is longest in this area. The total part of the eclipse
lasts for two spectacular minutes anywhere between Cairns and
Port Douglas. To the north and south, duration gets progressively
shorter and shorter until, near the southern and northern limits,
it only lasts for a few seconds. For folks living in or near
Innisfail, watch from at least 20km north of Innisfail say Babinda
or Bramston Beach to get a decent duration of about 1m 20s.

This map is a low-resolution
illustration and only intended to show the relative positions
of places mentioned in the text. High resolution maps and predictions
of all eclipse paths are available from the web site links provided
at the end of this document.

Location, Location
LocationAny place
with a good view of the east horizon will make a great place to watch
the eclipse. Though the beach immediately comes to mind, the tide will
probably be coming in as the eclipse progresses. Some beaches may
become covered by tides . New Moon occurs at 06:38. A high tide of
about 3m occurs mid-morning (9:06am) on the day of the eclipse in this
region. Tide height during totality will probably be about 2.3m. So the
tide will be low at 3am about the time you select your observing
location. High tide will be coming in during the eclipse and high tide
will occur about an hour after the total eclipse ends. Oak
beach might seem to be the perfect spot located on the beach and the
centreline but the following photograph shows why Oak Beach should be
avoided.

In the photo above I
tried to take the photo keeping the camera level with the ground in the
beach house yard. I was probably a touch low. The back yard
is more like 3.1m. In the photo below, I've constructed contours and
then using tide data, annotated the photo with times when the tide will
reach it.

Some beaches north of Cairns
do not get completely covered during a 3m high tide. These include
Kewarra beach, Trinity beach and Palm Cove. If you are just looking by
eye or using a camera and tripod, these beaches are ideal.

High ground might also
appeal. One very obvious spot is Rex Lookout on the Captain Cook
Highway. However, people stopping at the lookout have the
potential to cause traffic problems so the authorities have decided to
close the lookout during the eclipse.

Expert
observers who bring telescopes should probably retreat inland
a few kilometres to shelter from any onshore winds. The many
open fields between Skyrail and the airport should provide adequate
cover. These agricultural fields though unfenced, are private
property. Please treat any crop plantings with due repect. Use
the verges, don't trample the tilled fields and don't drive onto
ploughed soil. You might damage the plantings or become deeply
bogged.

Example of
an open field suitable for anyone wanting to get away from the
coast.

Charter boats will be
offering cruises to take people out to watch the eclipse at sunrise
from the boat or on diving platforms on ocean reefs followed
by reef viewing, diving or snorkelling after. These reef and
sky tours present a unique way to experience the eclipse. Be
aware that the reef platforms are pontoon platforms that will
move with the ocean swell. The boats are too small to be fitted
with stabilizers. If you are using any sort of telescope, binoculars
or camera and tripod, you should probably stay on solid ground.
You don't need to use binoculars or telescopes to enjoy an eclipse.
So much is going on around the whole sky many choose to just
look with the naked eye. If you just want to look and enjoy,
these reef and sky charters might be just the ticket.

Weather Prospects

November
isn't the sunniest month of the year but nor is it the cloudiest. It is
in the build up but definitely before the start of the monsoon.
Humidity causes
cloud build up during the days. Afternoon and evening showers and
thunderstorms are common. Fortunately mornings are typically fine and
sunny along
the coast but with some scattered cloud off the coast almost every
morning.
The rising moist air causes clouds to form along the tops of the
coastal mountain range so it's probably wise to stay clear of
places
like Mt Molloy, Mareeba, Atherton and Kuranda. No cyclone has ever
occurred in November in North Queensland in the time since records have
been kept.

Weather Information

1. The Australian Bureau of Meteorology http://www.bom.gov.au is a primary source of general weather information.

2. Jay Anderson is a Canadian Meteorologist who specializes in eclipse weather. His site is http://www.eclipser.ca He has a whole section about weather prospects for this November's eclipse

3. Andrew Cool's Skippy sky Astro weather forecast site has a
North Queensland map covering the eclipse. Skippy Sky is a graphical 2d
map representation of the GFS (Global Forecasting System) model data.
Goto http://www.skippysky.com.au click on Australia and then choose the Cairns tab. The eclipse path is marked on the map.

Eye SafetyA few minutes
after sunrise, the eclipse begins. The Sun first goes through
a partial eclipse that lasts for about an hour before the total
eclipse begins. During this time, there is great danger of eye
damage if you don't protect your eyes. The whole eclipse lasts
for about two hours.

The total part of the
eclipse lasts for about 2mins in the middle of the two hours.
During this time, the photosphere, the bright surface of the
Sun, is completely covered by the Moon so totality can be safely
observed without using eye protection. The total eclipse is only
as bright as a full Moon and regardless of what you might read,
there are no dangerous rays that will damage your eyes during
this period. The two phenomena known as diamond rings mark the
start and end of the safe period and it's only during the between
the two diamond rings that it is safe to look without eye protection.

............

The Sun goes through
an hour of partial eclipse before and an hour after the total
eclipse. During both periods, there is great danger of eye damage
occurring.

How to protect your
eyes during the partial eclipses?

During the partial eclipses
both before and after totality, you must use special
techniques to protect your eyes. Looking at the Sun at anytime
during an eclipse or even on a normal day can burn the retina
causing permanent eye damage. The Sun is no more dangerous during
a partial eclipse than it is on any other day. On a normal day,
if you glance at the Sun or get the Sun in your eyes for example
while you are driving, you don't go blind. But you don't stare
at the Sun. During the eclipse, you don't have to protect your
eyes from glancing contact with the Sun any more than you do
on a normal day. The problem is that during the eclipse, there
is a temptation to stare at the eclipse for extended periods
especially as the Sun gets covered. Staring can cause burns on
the retina leading to permanent blind spots.

Using found materials
from around the home as defacto solar filters is very dangerous.
These materials don't filter the dangerous UV and IR rays and
can lead to blind spots even though the image looks dark enough
to the eye. Examples of unsuitable filters include pinholes,
photographic film negatives, cd's/DVD's, smoked glass and silvered
confectionary wrappers among many others. There are no materials
found around the home that will safely filter the Sun's high
intensity light. Some of these materials might look similar to
solar filters but they are definitely not safe. The best
policy is to assume that if it hasn't been made for the purpose,
it isn't safe.

Even during the final
minute when the Sun is almost completely covered and the ambient
lighting begins to looks like like twilight, the energy in the
very thin crescent is more than capable of causing a permanent
burn to the retina.

There are two accepted
safe methods for watching a partial eclipse. One is to look through
some sort of specially made filter material, the other is to
use some sort of projection method.

Filters
Eclipse shades are special cardboard frame sunglasses with properly
made solar filters built-in. These should be available for purchase
at many tourist and retail outlets around Cairns. These are the
most convenient filtration method. Do read the instructions.
Some of these shades are not rated for continuous viewing but
for viewing 30 seconds at a time. A pair of eclipse shades will
probably cost less than $10.00. These cardboard glasses use special
filter materials that effectively cut all wavelengths of light
including the dangerous IR and UV that defacto materials pass
to your eyes. Your eyesight is definitely worth the investment.
Other suitable filters are a number 14 arc welding filter available
from welding suppliers or a special solar filters available from
astronomical suppliers designed to be attached to telescopes
or binoculars.

Girl in a bus,
Jinta, Gansu Province, China testing her eclipse shades before
the 2008 eclipse began

The oldest safe method
is the projection method. Cut the side out of a large cardboard
box. Punch a 5mm hole in the side.

The Sun will be rising
as the eclipse begins. Stand about 3-5m away from the east wall of a white
walled building. With your back to the Sun hold the card up so
that its shadow falls on the wall. In the middle you will see
a small image of the partially eclipsed Sun.

What will you see?
The Sun will rise at 5:34am. About ten minutes later the partial
eclipse will begin. If you are on the Cairns waterfront, the Sun will
remain hidden behind Cape Grafton for 15-20minutes. It will rise over
the cape about one third eclipsed. The dark disk of the Moon will
ingress upon the Sun's disk from the west which is the top when viewing
the rising Sun in the east. The appearance of the first half of
the eclipse up to the beginning of totality is illustrated in the gif
animation below. The partial eclipse will take 54 minutes. As totality
approaches, the solar crescent will become very thin. Though thin, it
is still too dangerous to look at without any eye protection.

About a minute or two
before the start of the total eclipse, look to the west. You
will see the Moon's shadow moving across the sky from west to
east. West to east may at first seem a little odd. Even though
the Moon rises in the east and sets west due to the Earth's rotation,
the Moon actually orbits the Earth from west to east. So the
shadow being cast by the Moon also travels from west to east.
The shadow will move slowly when it is near the western horizon,
very quickly as it passes overhead and to the east. When this
shadow reaches the Sun in the east the total eclipse begins.

0o5:34
a.m. Sunrise.-partial eclipse begins a few minutes later at 5:44am

During the minute or
so before the eclipse the lunar shadow covers the sky. The ambient
light will dim dramatically reducing by a factor of about a thousand.
If you have a really accurate time source, you can remove your
eclipse glasses about ten seconds before the start of the total
eclipse. The Moon's shadow by now will have moved right across
to cover the whole of the sky. When the front edge of the shadow
reaches the Sun, the diamond ring will form and the total eclipse
begins. The diamond ring is a bright ring of light surrounding
the dark lunar disk with one dazzling bright white point of light.

The diamond ring light
is the last little bit of the Sun's surface visible through the
deepest valley that points at Earth on the the edge of the Moon.
Even when this disappears, it won't. go completely dark, more
like a very deep twilight. Your eyes will quickly adjust to the
new low light level. As your eyes adjust, the Sun's corona will
become visible. The corona is composed of very hot electrically
charged gas - a plasma. The coronal gas has a temperature of
about a million degrees and it stretches millions of kilometres
out into space. The charged particles are distributed along and
reveal the Sun's magnetic field lines similar to the way your
science teacher at school might have used iron filings to reveal
the field of a magnet.

The corona will appear to
grow. This is just an illusion caused by two factors. As the umbra
replaces the penumbra in the sky around the Sun, the background sky
darkens rapidly allowing the faint corona to be mre visible. The
outer corona is fainter than the inner corona. As your eyes quickly
adapt to the dark mainly due to dilation of the pupils, they become
more sensitive so you are able to see fainter parts of the outer corona
so it seems to grow. Nonetheless, the effect is mesmerizing and if you
are observing the eclipse in the presence of a large crowd, you usually
hear one loud synchonized gasp from the crowd.

As totality ends, a
diamond ring dazzles you as it seems to explode from the opposite side
of the Moon to the first diamond ring. This one seems much brighter
than the first because your eyes are adapted to the dark. The
appearance of the second diamond ring is your signal to put your eye
protection back to work. Put on your eclipse shades or use your
projector and don't look directly at the Sun for the remainder of the
eclipse. The Moon spends another hour in partial eclipse as it
gradually uncovers the Sun. This time the disc will continue its motion
to the east and slide off downwards towards the horizon. The event is
all over by 7:40 am.

The times printed here are
average times for the area described. Mountains and valleys
around the edge of the Moon can change these times by many seconds.
Astronomers call the calculation of this change a lunar limb profile
correction or just limb correction. These times do not have limb
corrections applied. Your particular location may experience a change.

If
you have Google Earth on your computer, eclipse paths (.kmz files)
can be down loaded then overlaid onto Google Earth from Xavier
Jubier's web site. These come with an interactive tool that
calculates eclipse circumstances for the point at the centre
of the screen.

Bill Kramer's
Eclipse Chasers web
site has a javascript calculator for calculating local circumstances
for this eclipse for any latitude/longitude.